The stamp collection is one of the more unexpected bits of the Royal Collection. With the royal provenance attached some of it is basically priceless.
And don't forget the Faberge..........
HM owns two Easter eggs and a literal farmyard of faberge animals. Queen Alexandra loved Faberge - her sister the Tsarina basically had a standing order in and obvs one needs to keep up with sister. One year Edward VII got the Faberge team over in secret and they modelled the whole lot of animals at Sandringham and she got the lot for her birthday.